This quest is not available in game.
Bring 4 Wraith Essences and 1 Tainted Wraith Essence to Summoner Teli'Larien at the Sunspire on Sunstrider Isle.
Heed my words, young one - there is a taint about this island, and it is far more potent than the remnants of the Scourge.
I believe there is a true demonic presence on the isle.
West of here are the spires of Falthrien Academy. The arcane wraiths that infest it are a window to the source of demonic power. You are to bring me the essences of tainted and untainted wraiths.
In exchange for your obedience, I'll teach you how to summon an imp companion - your first of many as a warlock.